Muscarine modulates Ca2+ channel currents in rat sensorimotor pyramidal cells via two distinct pathways

Ansalan E. Stewart, Zhen Yan, D. James Surmeier, Robert Foehring

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

We used the whole cell patch-clamp technique and single-cell reverse transcription-polymerase chain reaction (RT-PCR) to study the muscarinic receptor-mediated modulation of calcium channel currents in both acutely isolated and cultured pyramidal neurons from rat sensorimotor cortex. Single- cell RT-PCR profiling for muscarinic receptor mRNAs revealed the expression of m1, m2, m3, and m4 subtypes in these cells. Muscarine reversibly reduced Ca2+ currents in a dose-dependent manner. The modulation was blocked by the muscarinic antagonist atropine. When the internal recording solution included 10 mM ethylene glycol-bis (β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) or 10 mM bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA), the modulation was rapid (τ(onset) ~ 1.2 s). Under conditions where intracellular calcium levels were less controlled (0.0-0.1 mM BAPTA), a slowly developing component of the modulation also was observed (τ(onset) ~ 17 s). Both fast and slow components also were observed in recordings with 10 mM EGTA or 20 mM BAPTA when Ca2+ was added to elevate internal [Ca2+] (~150 nM). The fast component was due to a reduction in both N- and P-type calcium currents, whereas the slow component involved L-type current. N- ethylmaleimide blocked the fast component but not the slow component of the modulation. Preincubation of cultured neurons with pertussis toxin (PTX) also greatly reduced the fast portion of the modulation. These results suggest a role for both PTX-sensitive G proteins as well as PTX-insensitive G proteins in the muscarinic modulation. The fast component of the modulation was reversed by strong depolarization, whereas the slow component was not. Reblock of the calcium channels by G proteins (at -90 mV) occurred with a median τ of 68 ms. We conclude that activation of muscarinic receptors results in modulation of N- and P-type channels by a rapid, voltage-dependent pathway and of L-type current by a slow, voltage-independent pathway.

Original languageEnglish (US)
Pages (from-to)72-84
Number of pages13
JournalJournal of Neurophysiology
Volume81
Issue number1
DOIs
StatePublished - Jan 1 1999

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Muscarine
Pyramidal Cells
Pertussis Toxin
Muscarinic Receptors
GTP-Binding Proteins
Egtazic Acid
Calcium Channels
Reverse Transcription
Calcium
Polymerase Chain Reaction
Ethylmaleimide
Muscarinic Antagonists
Acids
Ethylene Glycol
Patch-Clamp Techniques
Atropine
Ether
Cholinergic Agents
Neurons
Messenger RNA

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Physiology

Cite this

Muscarine modulates Ca2+ channel currents in rat sensorimotor pyramidal cells via two distinct pathways. / Stewart, Ansalan E.; Yan, Zhen; Surmeier, D. James; Foehring, Robert.

In: Journal of Neurophysiology, Vol. 81, No. 1, 01.01.1999, p. 72-84.

Research output: Contribution to journalArticle

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